Here's another theory that parallels Schindewolf's by applying a macromutational mechanism to mammalian evolution:

I don't see the parallels. To illustrate, here's a question for you to dodge:

Would the chromosomal rearrangements cited by Wesley (translocations, inversions, breaks, fusions, etc.) be more likely to cause "pretty much instant speciation" via huge changes in phenotype, or via an entirely genetic mechanism that's covered in undergraduate genetics courses, as well as in some advanced high-school genetics courses?